Freddy Cachazo

Research Interests

In recent years it has become clear that the scattering matrix of massless particles is a very special object. Massless particles are the backbone of our best theory of nature; the Standard Model of particle physics and gravity. In 2003, Witten succeeded in combining twistor theory and string theory to produce a new formulation for the scattering matrix of gauge bosons - massless particles of helicity plus or minus one. Since then finding a similar formulation for gravitons - particles with helicity plus or minus two - has been a very important open problem. In 2012, in collaboration with Y. Geyer (a PSI student), I found one such formulation. Not long after this first formulation was found, I found a second one with D. Skinner (a PI postdoctoral fellow). All these constructions are based on four dimensional kinematics. A natural question is whether similar constructions can be found in any dimension. Such a general formulation could lead to a deeper understanding of field theory in general. In 2013 and in collaboration with E. Yuan (a PI graduate student) and S. He (a PI postdoctoral fellow), I found such a construction. This is now known as the CHY construction and it gives tree-level scattering matrices of a variety of theories, including gluons and gravitons, in any dimensions as integrals over the space of n-punctured spheres. This new formulation has become an active area of research. In 2014 our group found CHY representations for theories such as Dirac-Born-Infeld and Galileons. Very recently we have found extensions of the theory of pions using soft limits which were previously hidden and become manifest using their CHY formulation.

Positions Held

September 2009 - June 2010 School of Natural Sciences. Institute for Advanced Study. Princeton NJ.
Member.